Such systems are known from U.S. Pat. No. 4,991,079, the content of which is here incorporated by reference and from U.S. Ser. No. 07/403,779, filed Sep. 8, 1989, continuation of Ser. No. 06/880,222 filed Jun. 30, 1986, now abandoned, the content of which is here incorporated by reference, both of which are commonly owned with the present application. Such systems use two ported memories. Although they are successful in reflecting data among a plurality of nodes, these systems have limitations which will become more readily apparent from the following description.